Shutter arrangement for a switchgear unit

ABSTRACT

Discloses a shutter arrangement for protecting the live stationary disconnect contacts of a switchgear unit from being accidentally engaged when the circuit breaker has been removed from its surrounding cubicle. The shutter-operating mechanism is a toggle-type mechanism that responds to circuit breaker withdrawal by moving into an overcenter locking position where the shutter covers the stationary disconnect contacts and is effectively locked.

United States Patent Charles D. Eichelberger Ridley Park, Pa.

Dec. 19, 1969 Oct. 5, 1971 General Electric Company Inventor Appl. No. Filed Patented Assignee SHUTTER ARRANGEMENT FOR A SWlTCHGEAR UNIT 5 Claims, 3 Drawing Figs. US. Cl 200/50 AA, 317/103 lnt.Cl l-l01h 9/20 Field of Search 200/50 AA; 317/103 References Cited 9 UNITED STATES PATENTS 1,566,935 12/1925 Trencham et al 317/103 X 1,729,864 10/1929 Brown 317/103 2,340,082 1/1944 Sauers 317/103 3,277,252 12/1963 Beddoe et a1. 200/50 AA 3,397,293 8/1968 Darrow et a1. 200/50 AA Primary Examiner-Robert K. Schaefer Assistant Examiner-M. Ginsburg Attorneys-.1. Wesley Haubner, William Freedman, Frank L.

Neuhauser, Oscar B. Waddell and Joseph B. Forman ABSTRACT: Discloses a shutter arrangement for protecting the live stationary disconnect contacts of a switchgear unit from being accidentally engaged when the circuit breaker has been removed from its surrounding cubicle. The shutteroperating mechanism is a toggle-type mechanism that responds to circuit breaker withdrawal by moving into an overcenter locking position where the shutter covers the stationary disconnect contacts and is effectively locked.

This invention relates to a switchgear unit comprising a cubicle and a circuit breaker movably mounted therein and relates, more particularly, to a shutter arrangement which protects the live stationary disconnect contacts of such a unit from being accidentally engaged with the circuit breaker has been removed from the cubicle.

In such shutter arrangements, a shutter has a blocking position in front of the stationary disconnect contacts wherein it acts as a barrier for blocking accidental engagement with these contacts. It will be apparent that if the shutter, with little thought, can be easily moved out of its blocking position, e.g., by a careless workman, then accidental engagement with the disconnect contacts is not being sufliciently prevented.

An object of the invention is to provide a simple and inexpensive shutter operating mechanism that effectively locks the shutter in its blocking position during the time the circuit breaker is removed from the cubicle, thus minimizing the likelihood of accidental engagement with the live stationary disconnect contacts.

Another object is to provide a shutter operating mechanism which, though effectively locked when the circuit breaker is removed, can be readily unlocked without damage or disassembly by a knowledgeable maintenance man who requires access to the stationary disconnect contacts.

Still another object is to provide a shutter operating mechanism which is free of any spring coupling that might allow the shutter to be easily displaced from its blocking posi tion by deflecting the spring.

In carrying out the invention in one form, we provide a pivotally mounted shutter and a shutter-operating mechanism coupled to the shutter and operable to pivot the shutter into a blocking position covering the stationary disconnect contacts when the circuit breaker is moved from a fully connected position into a partially withdrawn position. The shutter-operating mechanism comprises an overcenter toggle linkage through which shutter-operating forces are transmitted to the shutter. This toggle linkage moves through dead center into an overcenter locking position when the shutter is moved into its blocking position, thereby locking the shutter against movement out of said blocking position by forces applied directly to the shutter.

For a better understanding of the invention, reference may be had to the following description taken in conjunction with the accompanying drawings, wherein:

FIG. I is a side elevational view partly in section of a switchgear unit embodying one form of the invention.

FIG. 2 is a sectional view taken along the line 2-2 of FIG.

FIG. 3 is a front end view of a modified switchgear unit embodying another form of the invention.

Referring now to FIG. I, there is shown a switchgear unit comprising a metal cubicle l2 and a removable, or drawout, circuit breaker unit 14 mounted on suitable wheels 16. The wheels allow the circuit breaker unit to be rolled horizontally from the withdrawn position shown to a fully inserted position inside the cubicle. In the fully inserted position, a set of socket-type contacts 18 carried by movable circuit breaker unit on forwardly projecting conductive studs 19 fully engage a set of plug-type stationary contacts 20 suitably supported on the cubicle. Mating pairs of contacts 18 and 20 when fully engaged form the terminals for a power circuit (not shown) extending throughv the circuit breaker unit and controlled thereby. In the embodiment illustrated in FIG. 1, the lower disconnect contacts are connected to a load, and the upper disconnect contacts are connected to a live bus and are normally energized.

The circuit breaker can be placed in operation by pushing the movable unit 14 into the cubicle a predetermined distance and by then moving it to the right to its fully connected position by means of a suitable racking mechanism (not shown). This racking mechanism may be of any suitable conventional form, e.g., the form shown and claimed in U.S. Pat. No.

I 3,440,371-Netzel et al., assigned to the assignee of the present invention. When the circuit breaker is in its withdrawn position shown, it is necessary that a suitable shutter cover the stationary disconnect contacts to prevent anyone working inside the cubicle from accidentally engaging them. I show such a shutter at 24 located in a blocking position in front of the stationary contacts 20. This shutter can be either of insulating material or metal at ground potential. Tubes 25 of insulating material surround the stationary contacts in radially spaced relationship and further shield then from accidental engagement.

Shutter 24 is movably mounted so that under certain circumstances it can be displaced from its blocking position shown. For movably mounting the shutter 24, a horizontally extending bracket 26 is connected thereto at its upper end,

and this bracket 26 is pivotally mounted on a vertically extending stationary pivot 28. Thus, the shutter is mounted for pivotal movement about a vertical axis formed by pivot pin 28.

For operating the shutter 24, I provide a shutter-operating mechanism 29 comprising a pair of toggle links 30 and 32 pivotally joined together at one end by a knee 34. At its opposite end, one of the toggle links 32 is pivotally connected by means of a pivot 33 to the shutter bracket 26. The other toggle link 30 is keyed to a gear shaft 35 and is arranged to pivot about the axis of the shaft 35 when the shaft rotates. Shaft 35 is joumaled in a suitable bearing that is mounted on stationary cubicle 12. When shalt 35 is rotated in a counterclockwise direction from its solid line position of FIG. 2, it collapses the toggle 30, 32, 34, causing it to pass through its dotted line intermediate position into a dot-dash line fully open position. This pivots the shutter in a clockwise direction about pivot 28 from its solid-line closed position through the dotted line intermediate position, into its fully open dot-dash line position.

The shutter is returned to its solid-line position of FIG. 2 from its fully open dot-dash position shown by rotating shaft 35 in an opposite or clockwise direction. This extends the toggle, causing it to pass through its intermediate position into its solid-line closed position.

An important feature of the invention is that the toggle 30, 32, 34 when in its solid-line position is in an overcenter condition wherein the shutter is effectively locked against reverse movement, In this regard, note that during the abovedescribed shutter-closing operation the knee 34 of the toggle passes beyond a reference line 37 connecting the pivot axes 35 and 33 and representing dead center of the toggle. When the toggle is in this overcenter position, any force applied directly to the shutter and tending to rotate it clockwise about pivot 28 tends to drive the toggle further past dead center. Any such further motion past center is blocked by a stop 40 on the toggle link 32 which engages the other toggle link 30 to prevent any further overcenter collapsing motion of the toggle past its solid-line position. The importance of this feature will soon be explained in more detail. Any position of the toggle before reaching dead center 37 during shutter closing is referred to herein as an undercenter position.

For transmitting rotary motion to the toggle-operating shaft 35, a set of bevel gears 50 and 52 is coupled thereto. Driven bevel gear 50 is keyed to shaft 35, and driving bevel gear 52 is keyed to a drive shaft 54 journaled in a stationary bracket 56. Also keyed to drive shaft 54 is a crank arm 58.

For transmitting motion to the bevel gears 50, 52, a cam plate 60 is pivotally mounted at 64 on the wall of cubicle 12. The free end of cam plate 60 is connected to the crank 58 by means of an operating rod 66 pivotally connected at its opposite ends to the cam plate 60 and crank arm 58 by pivot pins 69 and 70, respectively, The operating rod 66 is adjustable in length to provide for suitable adjustments of the cam plate 60 with respect to the toggle linkage 30, 32, 34.

The cam plate 60 is arranged to be operated in response to motion of the movable circuit breaker unit 14 within cubicle 12. In this respect, note that the cam plate contains an openended cam slot 74 that is adapted to receive a pin or roller 72 effectively fixed to one side of the movable circuit breaker unit. When movable circuit breaker unit 14 is completely withdrawn from the cubicle 112, the cam plate 60 occupies the position of FIG. I and the shutter 24 is accordingly fully closed as shown. When the circuit breaker unit is moved to the right from its position of FIG. 1 toward its fully inserted position, pin 72 enters the cam slot 74. The first part 75 of the cam slot 74 is a dwell portion, and, as a result, the pin 72 can be moved into the dotted line position 80 of FIG. 1 without causing any motion of the cam plate. The position occupied by the circuit breaker when the pin 72 is in its dotted line position of FIG. 1 is known as the test position of the circuit breaker.

When the movable circuit breaker unit is moved further to the right from its test position the pin 72 engages an active portion 76 of the cam slot 74, thereby pivoting the cam plate 60 counterclockwise about pivot 64. This counterclockwise motion of the cam plate 60 is transmitted through parts 66, 58, 52, 50 to the toggle-operating shaft 35, thus operating the toggle 30, 32, 34 to swing the shutter from its closed position to its fully open position. v

When the pin 72 has reached a point near the right-hand end of the active portion 76 of cam slot 74, the movable disconnect contacts 18 have reached their dotted line position 18a, where they are spaced only a short distance from the stationary disconnect contacts 20. The shutter 24, being near its fully open position, is no longer between the movable and stationary disconnect contacts. Thus, further movement to the right of the movable circuit breaker unit drives the movable disconnect contacts I8 into engagement with stationary disconnect contacts 20 without interference from shutter 24. During such movement of the movable circuit breaker unit, the pin 72 first moves to the end of active portion 76 of the cam slot, thereby completing opening of the shutter. Pin 72 then moves along another dwell portion 78 of the cam slot, and such motion of the pin produces no additional movement of the shutter.

When the circuit breaker is withdrawn from its fully connected position, the above-described sequence of events is repeated in reverse order. That is, initial withdrawal of the circuit breaker produces no shutter motion. Further withdrawal of the circuit breaker causes pin 72 acting in the active portion of cam slot 74 to drive the cam plate 60 counterclockwise, thereby returning the shutter to its solid-line closed position of FIG. 2. The circuit breaker can then be completely withdrawn from the cubicle without further atfecting the shutter position.

When the circuit 'breaker is in its test position, or is completely withdrawn from the cubicle, the shutter cannot be operated out of its closed position by a force applied directly thereto in view of the above-described locking action of the toggle 30, 32, 34 when in its overcenter position that it occupies when the shutter is fully closed. This prevents one working in the cubicle from accidentally brushing against or otherwise engaging the live stationary contacts of the switchgear unit. It is particularly important to provide such locking action in those arrangements where the shutters of the switchgear unit are pivotally mounted since gravity ordinarily interferes less with opening a pivotally mounted shutter than one that is slidably mounted and must be lifted to effect opening.

If for some special reason it is desired to have access to the stationary contacts during this period when the circuit breaker is removed, such access can be had by lifting the cam plate 60 out of its position of FIG. I. This operates the toggle 30, 32, 34, to move shutter 24 into its open position. As soon as the workman releases the cam plate 60, it will fall by gravity into its solid line position, thereby closing the shutter. Because the special step of lifting cam plate 60 is a necessary precondition to opening the shutter, it is highly unlikely that a careless workman will accidentally open the shutter. Moreover, considerable force on the cam plate is required to drive the toggle 30, 32. 34 from its overcenter position through dead center, and this further reduces thepossibility of an unintentional opening of the shutter. The above-described lifting of cam plate 60 can, of course, be efiected by applying a force to rod 66 or any other part of the shutter operating mechanism on the normally driving side of toggle linkage 30, 32, 34.

FIG. shows a modified form of the invention and is a view looking into the cubicle from its open end toward the stationary disconnect contacts when the circuit breaker is removed from the cubicle. In the embodiment of FIG. 3, three stationary disconnect contacts, which are respectively connected to the buses of a three-phase circuit, are shown in dotted lines at 100, 102, and 104. Three stationary disconnect contacts, which are respectively connected to the load conductors of the three-phase circuit, are shown in dotted lines at 106, 108 and 110. The contacts 100, 102, 104 are located in a vertically extending first plane, and the contacts 106, 108, and 1110 are located in a vertically extending second plane horizontally spaced from the first plane. This disconnect contact arrangement corresponds to that present in the switchgear unit shown and claimed in U.S. Pat. No. 3,397,293-Darrow et al., assigned to the assignee of the present invention.

Two separate shutters are provided, one for the busside stationary disconnect contacts and one 116 for the loadside stationary disconnect contacts. Each of these shutters is operated by a toggle-type operating mechanism 30, 32 corresponding to the identically designated operating mechanism of FIGS. 1 and 2. Each of these toggle operating mechanisms is operated by a set of bevel gears 50, 52, and operating rod 66 and a cam plate 60 corresponding to identically designated parts in FIG. 1. Two pins, each corresponding to pin 72 in FIG. 1, are provided in opposite sides of the movable circuit breaker unit for operating the cam plates 60 in response to circuit breaker motion in the same manner as explained relative to FIG. 1. The mechanisms are adjusted so that such operation of the cam plates produces substantially simultaneous operation of the shutters.

When the circuit breaker is removed from the cubicle, as shown in FIG. 3, each of the toggle mechanisms 30, 32 is in an overcenter condition, where it locks its associated shutter in its closed position in front of its associated stationary contacts.

In certain switchgear arrangements the load-side disconnect contacts are deenergized when the circuit breaker is removed from the cubicle. It may sometimes by desirable to work on these deenergized load-side stationary disconnect contacts without deenergizing the bus-side stationary disconnect contacts. The arrangement of FIG. 3 permits this to be done without exposing the bus-side stationary contacts. In this regard, the load-side shutter 116 can be opened independently of the bus-side shutter 115 by raising the cam plate 60 at the right-hand side of the cubicle, as explained in connection with FIG. 1. The bus-side shutter I15 remains in its closed position, thus shielding the live disconnect contacts 100, I02, I04 against accidental contact while the load-side contacts are exposed.

While I have shown and described particular embodiments of my invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from my invention in its broader aspects; and I, therefore, intend herein to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a switchgear unit comprising a cubicle having stationary disconnect contacts mounted thereon, a circuit breaker movable into and out of said cubicle and having movable disconnect contacts that engage said stationary disconnect contacts when said circuit breaker is moved completely into said cubicle and disengage said stationary contacts when said circuit breaker is moved out of said cubicle, the combination:

a. a shutter, means pivotally mounting said shutter on said cubicle such that said shutter has a nonblocking position that allows said movable and stationary disconnect contacts to engage when said circuit breaker is fully inserted into said cubicle,

b. a shutter-operating mechanism coupled to said shutter mounting means and operable to pivot said shutter into a blocking position covering said stationary disconnect contacts when said circuit breaker is moved into a partially withdrawn position within said cubicle where said movable and stationary disconnect contacts are disengaged,

c. and means coupled to said shutter-operating mechanism and responsive to motion within said cubicle of a part coupled to said movable circuit breaker for supplying shutter-operating forces to said shutter-operating mechanism,

d. said shutter-operating mechanism comprising an overcenter toggle linkage connected to said shutter-mounting means through which shutter-operating forces are transmitted to said shutter,

e. said toggle linkage moving through dead center into an overcenter locking position vwhen said shutter is moved into its blocking position,

t. a force applied directly to said shutter in a direction to move said shutter from its blocking to its nonblocking position acting on said toggle linkage in a direction to drive the toggle linkage further overcenter from said overcenter locking position, and

g. blocking means for blocking motion of said toggle linkage further overcenter from said overcenter locking position upon application of said force to move said shutter to its nonblocking position thereby locking said shutter against movement out of said blocking position by forces applied directly to said shutter.

2. The combination of claim 1 in which said overcenter toggle linkage comprises a first link pivotally mounted on said cubicle, a second link pivotally connected to said first link at one point and to said shutter mounting means at a point spaced therefrom, said first link constituting a driving link that is actuated in response to movement of said circuit breaker, said first and second links forming a toggle that occupies an undercenter position when said circuit breaker is fully inserted and that moves through a dead center position into an overcenter position in response to said circuit breaker movement out of its fully inserted position into a contact disengaged position.

3. The combination of claim 1 in which said shutter-operating mechanism can be operated when said circuit breaker is removed from the cubicle by force applied to the normally driving end of said toggle linkage.

4. The combination of claim 1 in which:

a. said cubicle has additional stationary disconnect contacts and said circuit breaker has additional movable disconnect contacts, the additional disconnect contacts being load-side disconnect contacts,

b. an additional shutter corresponding to said first-mentioned shutter is provided for said additional stationary disconnect contacts,

c. an additional shutter-operating mechanism, means for rendering said additional shutter-operating mechanism responsive to motion of a part coupled to said movable circuit breaker for operating said additional shutter substantially simultaneously with said first-mentioned shutter, and

d. said additional shutter-operating mechanism is operable independently of said first shutter-operating mechanism when the circuit breaker has been withdrawn from said cubicle, thereby permitting access to said additional stationary disconnect contacts without exposing the first stationary disconnect contacts.

5. A switchgear unit as defined in claim 1 in which:

a. said stationary disconnect contacts include three bus-side disconnect contacts mounted in a generally vertically extending first plane and three load-side disconnect contacts mounted in a generally vertically extending second plane spaced horizontally from said first plane,

b. said first mentioned shutter is provided for said bus-side disconnect contacts and an additional shutter corresponding to said first mentioned shutter is provided for said load-side disconnect contacts,

c. and additional shutter-operating mechanism, means for rendering said additional shutter-operating mechanism responsive to motion of a part coupled to said movable circuit breaker for operating said additional shutter substantially simultaneously with said first-mentioned shutter,

d. said additional shutter-operating mechanism is operable independently of said first shutter-operating mechanism when the circuit breaker has been withdrawn from said cubicle, thereby permitting access to said load-side disconnect contacts without exposing said bus-side disconnect contacts,

e. said first shutter being mounted for pivotal motion about a first vertical axis and covering said bus-side disconnect contacts when in closed position, and

f. said additional shutter being mounted for pivotal motion about a second vertical axis spaced from said first axis and covering said load-side disconnect contacts when in closed position. 

1. In a switchgear unit comprising a cubicle having stationary disconnect contacts mounted thereon, a circuit breaker movable into and out of said cubicle and having movable disconnect contacts that engage said stationary disconnect contacts when said circuit breaker is moved completely into said cubicle and disengage said stationary contacts when said circuit breaker is moved out of said cubicle, the combination: a. a shutter, means pivotally mounting said shutter on said cubicle such that said shutter has a nonblocking position that allows said movable and stationary disconnect contacts to engage when said circuit breaker is fully inserted into said cubicle, b. a shutter-operating mechanism coupled to said shutter mounting means and operable to pivot said shutter into a blocking position covering said stationary disconnect contacts when said circuit breaker is moved into a partially withdrawn position within said cubicle where said movable and stationary disconnect contacts are disengaged, c. and means coupled to said shutter-operating mechanism and responsive to motion within said cubicle of a part coupled to said movable circuit breaker for supplying shutter-operating forces to said shutter-operating mechanism, d. said shutter-operating mechanism comprising an overcenter toggle linkage connected to said shutter-mounting means through which shutter-operating forces are transmitted to said shutter, e. said toggle linkage moving through dead center into an overcenter locking position when said shutter is moved into its blocking position, f. a force applied directly to said shutter in a direction to move said shutter from its blocking to its nonblocking position acting on said toggle linkage in a direction to drive the toggle linkage further overcenter from said overcenter locking position, and g. blocking means for blocking motion of said toggle linkage further overcenter from said overcenter locking position upon application of said force to move said shutter to its nonblocking position thereby locking said shutter against movement out of said blocking position by forces applied directly to said shutter.
 2. The combination of claim 1 in which said overcenter toggle linkage comprises a first link pivotally mounted on said cubicle, a second link pivotally connected to said first link at one point and to said shutter mounting means at a point spaced therefrom, said first link constituting a driving link that is actuated in response to movement of said circuit breaker, said first and second links forminG a toggle that occupies an undercenter position when said circuit breaker is fully inserted and that moves through a dead center position into an overcenter position in response to said circuit breaker movement out of its fully inserted position into a contact disengaged position.
 3. The combination of claim 1 in which said shutter-operating mechanism can be operated when said circuit breaker is removed from the cubicle by force applied to the normally driving end of said toggle linkage.
 4. The combination of claim 1 in which: a. said cubicle has additional stationary disconnect contacts and said circuit breaker has additional movable disconnect contacts, the additional disconnect contacts being load-side disconnect contacts, b. an additional shutter corresponding to said first-mentioned shutter is provided for said additional stationary disconnect contacts, c. an additional shutter-operating mechanism, means for rendering said additional shutter-operating mechanism responsive to motion of a part coupled to said movable circuit breaker for operating said additional shutter substantially simultaneously with said first-mentioned shutter, and d. said additional shutter-operating mechanism is operable independently of said first shutter--operating mechanism when the circuit breaker has been withdrawn from said cubicle, thereby permitting access to said additional stationary disconnect contacts without exposing the first stationary disconnect contacts.
 5. A switchgear unit as defined in claim 1 in which: a. said stationary disconnect contacts include three bus-side disconnect contacts mounted in a generally vertically extending first plane and three load-side disconnect contacts mounted in a generally vertically extending second plane spaced horizontally from said first plane, b. said first mentioned shutter is provided for said bus-side disconnect contacts and an additional shutter corresponding to said first mentioned shutter is provided for said load-side disconnect contacts, c. and additional shutter-operating mechanism, means for rendering said additional shutter-operating mechanism responsive to motion of a part coupled to said movable circuit breaker for operating said additional shutter substantially simultaneously with said first-mentioned shutter, d. said additional shutter-operating mechanism is operable independently of said first shutter-operating mechanism when the circuit breaker has been withdrawn from said cubicle, thereby permitting access to said load-side disconnect contacts without exposing said bus-side disconnect contacts, e. said first shutter being mounted for pivotal motion about a first vertical axis and covering said bus-side disconnect contacts when in closed position, and f. said additional shutter being mounted for pivotal motion about a second vertical axis spaced from said first axis and covering said load-side disconnect contacts when in closed position. 